BOSTON  A species of beetle never before seen in North America has been discovered in a Massachusetts forest, but the Asian insect does not appear to pose an ecological threat, experts said Monday.

Twenty-two beetles belonging to the Xyleborus seriatus species of ambrosia beetle were found in April in traps set by state forestry workers in Southborough, about 25 miles west of Boston. Two or three more were trapped in nearby Stow.

The insects were sent to Cornell University to be studied.

They may have "hitchhiked" to the United States on wooden crates shipped from Asia, Cornell entomologist Richard Hoebeke said.

"My guess is that it has been around awhile and simply gone undetected because nobody was looking for it," said Hoebeke, who announced the finding in an e-mail to colleagues on July 20.

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Each year, a dozen species of insects on average are discovered for the first time in the U.S., he said.

Some insects, such as the hemlock wooly adelgid, emerald ash borer and Asian longhorn beetle, can wreak havoc on wildlife habitat. However, most ambrosia beetles feed on fungi in dead or dying trees, not healthy ones.

"So far, it's not a cause for concern," said Glenn Rosenholm, regional spokesman for the U.S. Forest Service.

The new beetle is about three millimeters long and has brown legs and wings. Scientists are thinking about naming it the "Southborough beetle."